As more and more computers have become interconnected through various networks such as the Internet, computer security has become increasingly more important, as abuse by malicious computer users has greatly increased, particularly from invasions or attacks delivered over a network or over an information stream. As those skilled in the art will recognize, these attacks come in many different forms, including, but certainly not limited to, computer viruses, computer worms, system component replacements, spyware, adware, denial of service attacks, even misuse/abuse of legitimate computer system features, all of which exploit one or more computer system vulnerabilities for illegitimate purposes. While those skilled in the art will realize that the various computer attacks are technically distinct from one another, for purposes of the present invention and for simplicity in description, all malicious computer programs will be generally referred to hereinafter as computer malware, or more simply, malware.
Malware may become resident on a computer using a number of techniques. For example, a computer connected to the Internet may be attacked so that a vulnerability on the computer is exploited and the malware is delivered over the network as an information stream. By way of another example, malware may become resident on a computer using social engineering techniques. For example, a user may access a resource such as a Web site and download a program from the Web site to a local computer. While the program may be described on the Web site as providing a service desirable to the user; in actuality, the program may perform actions that are malicious.
When a malware becomes resident on a computer, the adverse results may be readably noticeable to the user, such as system devices being disabled; applications, file data, or firmware being erased or corrupted; or the computer system crashing or being unable to perform normal operations. However, some malware perform actions that are covert and not readily noticeable to the user. For example, spyware typically monitors a user's computer habits, such as Internet browsing tendencies, and transmits potentially sensitive data to another location on the network. The potentially sensitive data may be used in a number of ways, such as identifying a commercial product that matches the observed tendencies of the user. Then the spyware or an associated adware program may be used to display an advertisement to the user that promotes the identified commercial product. Since the advertisement interrupts the normal operation of the computer, the actions performed by the spyware may not be desirable to the user. Yet another pernicious aspect of many, though not all, computer malware is that an infected computer system is used to infect other computers.
A traditional defense against computer malware, and particularly computer viruses and worms, is antivirus software. Generally described, antivirus software scans data, looking for identifiable patterns associated with known computer malware. Frequently, this is done by matching patterns within the data to what is referred to as a “signature” of the malware. One of the core deficiencies in this malware detection model is that an unknown computer malware may propagate unchecked in a network until a computer's antivirus software is updated to identify and respond to the new computer malware.
When a malware infection occurs, the infection may be handled or managed in one of many different ways. Preferably, the infected computing device is capable of being “cleaned” so that the malware is no longer resident. However, in some instances, the malware may be configured to employ self-preservation techniques to resist being cleaned. In this instance, cleaning the computing device may not be feasible or may only be possible with a software update. Alternatively, files associated with the malware may be deleted from the computing device. However, as known to those skilled in the art and others, some malware attach to innocuous “hosts” which contain user data that will be lost if an infected file is deleted.
In yet another alternative, the malware may be “quarantined.” Typically, a quarantine occurs when data associated with the malware is altered to prevent execution of the malware. Quarantining malware is especially useful when a file may have been incorrectly identified as malware, the user wants to delay cleaning a file until a later time, or an infected file contains user data that needs to be saved. In some existing systems, a quarantined file is both prevented from executing program code and concealed from antivirus software that scans a computing device for malware. For example, one method of implementing a quarantine includes moving a file to a quarantine folder along with associated metadata that describes the location of the file. Among other things, the quarantine folder has established settings that prevent files from “executing” program code. To conceal the quarantined file from antivirus software, the data in the file is typically encoded. As a result, the file is not capable of causing harm to a computing device and will not be identified as malware if scanned by antivirus software.
Identification of a file or content item as “malware” by antivirus software, based upon a ‘signature’ of the malware has various deficiencies. First, unknown computer malware may propagate undetected in a network until a computer's antivirus software is updated to identify and respond to the new computer malware. To help lessen the likelihood of this problem, a signature can be released as early as possible. However, protection technologies that are based on heuristics or signatures often suffer from false positives that run the risk of purging valid content. This problem is most noticed during the first few hours after new malware is released to the wild, while the level of information about the malware and potential side effects of its deletion is limited. To mitigate this problem protection technology vendors typically delay the release of a new signatures or heuristic patterns until the malware is fully understood and a comprehensive test pass is completed and some opt to tune the heuristics and signatures to minimize false positives with the side effect of limiting the ability to detect malware. The impact of these mitigations is an increased window of exploit from the time malware is released in the wild until an asset is protected from that malware.